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Biological Monitoring Background
[Research Methodology]

Biological monitoring can inexpensively screen for problems that are not specifically tested for using common chemical kits. The presence of heavy metals, pesticides, herbicides, and other toxins in a stream may be indicated by a lack of biodiversity in a stream. Since certain organisms can tolerate more pollution than others, the greater the variety of organisms - the better the water quality. Biological monitoring can also indicate the presence of problems that extend over time.

The organisms that live in a stream are affected by the quality of the water in the stream. Some aquatic organisms, such as fish and frogs, can leave a polluted stretch of a stream; other organisms cannot. The organisms that cannot leave can be viewed as indicator organisms. Some pollutants are only in the water for a short period of time before they dilute out or wash downstream. These short term events might not show up in testing but they can have a dramatic impact on the organisms living in the stream. The presence of indicator organisms tells us a history of water quality in the stream.

Benthic macro-invertebrates are good indicator organisms and can be used to determine the health of a stream. Benthic means bottom dwelling, macro means large enough to be seen, and invertebrate means an animal without a backbone. Most benthic macro-invertebrates are aquatic insects or the aquatic stages of insects. Examples include stonefly nymphs, mayfly nymphs, caddisfly larvae, dragonfly nymphs, and midge larvae. Also benthic macro-invertebrates include such things as mollusks, crustaceans and worms. Identification key

Benthic macro-invertebrates are good indicator organisms because:

1. they are sensitive to physical and chemical changes in their habitat.

2. they cannot easily escape pollution in their environment, and

3. they are easily collected and classified.

The most common way to collect benthic macro-invertebrates is to use a kick net. The net is placed in a riffle. The rocks in a three foot square area in front of the net are turned over and scrubbed to free the invertebrates from the stream bed so that they can be caught in the net. Once the organisms have been caught, they are identified and counted.

The Stream Study provides a method to determine the water quality of a stream based on the collection and identification of stream-bottom macroinvertebrates. The Stream study also provides a useful IDENTIFICATION KEY for common stream-bottom macroinvertebrates.

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